The Temple of Sinnoh (Japanese: シンオウ神殿 Sinnoh Temple) is a location at the peak of Mount Coronet in the Coronet Highlands of Hisui, built as a monument to Arceus, also known as almighty Sinnoh. At the entrance of the temple are statues of the ancient hero's Pokémon: Wyrdeer, Kleavor, Ursaluna, Hisuian Lilligant, Basculegion, Hisuian Arcanine, Sneasler, Hisuian Electrode, Hisuian Braviary, and Hisuian Avalugg.
Fixtures modeled after Arceus's likeness such as its golden cross-like wheel and head are emblazoned on the temple's structure.
In present-day Sinnoh, the temple's ruins are known as the Spear Pillar.
The player first travels to the Temple of Sinnoh to prevent Galaxy Team Commander Kamado from recklessly trying to deal with the Pokémon sighted at the space-time rift above Mount Coronet. After being defeated in battle, Kamado sees the error of his ways and apologizes for banishing the player from Jubilife Village. At the end of the temple, either Dialga (if the player chose Adaman during Mission 14) or Palkia (if the player chose Irida during Mission 14) will then emerge from the space-time rift. The player will try to subdue the Legendary Pokémon with the Red Chain created by the lake guardians, but fails, forcing them to fight and catch it.
After the player has caught the Legendary Pokémon, its counterpart will appear and force the player to retreat. Once the player has obtained the Origin Ball, they return to the temple to face it, accompanied by the Legendary Pokémon captured earlier. The opposing Legendary Pokémon transforms into its Origin Forme, destroying the temple and all its statues in the process, and must be quelled using balms before the player can use the Origin Ball to catch it.
During the post-game, the player returns to the ruins of the temple, where Volo reveals that he was the one who sought out Giratina and had it tear open the space-time rift to anger Dialga/Palkia, ultimately causing the player's arrival in Hisui. Holding the last of the 18 Plates, he challenges the player to get the other 17 Plates from them so he can meet Arceus and use its power to recreate the world. After being defeated, he summons Giratina to his aid, forcing the player to defeat it as well. Once Giratina is defeated, Volo hands the player the last Plate and leaves, swearing to create his new world no matter how many centuries it will take.
Once the player has caught at least one of every non-Mythical Pokémon in Hisui, they return to the temple once again and play the Azure Flute, revealing a glowing stairway to the Hall of Origin, where Arceus awaits them.
After defeating Arceus, the player can return to the Temple of Sinnoh for rematches with Arceus, as well as Origin Forme Dialga or Palkia.
According to Ingo, the temple was built a long time ago using stone mined out of the Ancient Quarry. According to Old Verse 11, both people and Pokémon worked together to mine the stone, but humans were ultimately responsible for carving the statues of the ancient hero's Pokémon.
The Temple of Sinnoh is located at the very peak of Mount Coronet, although the north side of the temple stands above a vast snowy valley surrounded by mountain ranges of nearly equal height. It stands in the northwest corner of the Coronet Highlands, completely surrounded by Cloudcap Pass. Since the northern section of Cloudcap Pass is completely impassable, the only known entrance to the Temple is through the Stone Portal, a small straight tunnel that passes underneath it. After exiting the Stone Portal, there is a single straight trail upwards to the south side of the Temple. The path widens twice, once halfway up the trail and again at the base of the Temple itself.
Dialga and Palkia are coded to never be Shiny.
- As a member of the Diamond Clan
The following applies if the player picked Adaman during Mission 13: "Disaster Looming".
Dialga can be caught during Mission 17: "Atop Mount Coronet", which becomes available after the player forges the Red Chain from the materials obtained during the trials of the lake guardians.
Palkia can be caught in its Origin Forme during Mission 18: "The Counterpart" after the players catches Dialga. It reverts to its normal form after being caught.
- As a member of the Pearl Clan
The following applies if the player picked Irida during Mission 13: "Disaster Looming".
Palkia can be caught during Mission 17: "Atop Mount Coronet", which becomes available after the player forges the Red Chain from the materials obtained during the trials of the lake guardians.
Dialga can be caught in its Origin Forme during Mission 18: "The Counterpart" after the player catches Palkia. It reverts to its normal form after being caught.
Both Pokémon of Myth can be rematched in their Origin Formes at any point after the player catches Arceus. They cannot be caught and must be defeated.